The present invention relates to a method and an apparatus for producing tubular hollow items, in particular for containers, from card material or the like.
Within the scope of the invention, card material is also understood to mean a flat card which is laminated at least on one side, but preferably on both sides, with a plastic film. In particular, this is PE-coated card. However, the invention also includes all other flat or film-like materials, in particular single or multiple layer plastic films or foldable composite materials with aluminium coating. The plastic lamination is hot bonded or welded after the connection regions of the blank have been placed one on top of the other so that they overlap. When a pure card material is used, a weldable plastic intermediate layer is used in the form of a strip or a bond, for example by means of a hot adhesive or the like.
Methods and apparatuses of the above type are known especially in the production of packages for liquids. In this case, tubular hollow items are produced from a card material, are subsequently closed at one end, filled and, in a final step, also closed at the second end.
In DE-A 22 335 111, for example, a method and an apparatus for winding a multicomponent web to form a cylindrical hollow item from card material is disclosed, according to which the web, unwound from a roll, is partially inserted into a slotted sleeve in which a tube is rotatably arranged as a mandrel and, together with the sleeve, forms a receiving space. By means of a rotational movement, a section of the web is wound around the mandrel in the receiving space and is subsequently conveyed out of the bending station. To increase the efficiency of the apparatus, four slotted sleeves are in use, offset in cycles on a large wheel, as a result of which, however, the apparatus is mechanically complex and the constructional size increases considerably. Moreover, one sleeve remains unused, seen over one revolution of the wheel, by virtue of the principle, which impairs the degree of utilization of the system. Adaptation to cross-sectional areas of the hollow items other than round is also not possible. Furthermore, the apparatus described is used only for producing diaphragms. It does not provide for any connection of the cylindrical hollow item in the overlap region at longitudinal edges of the blank running parallel to one another. Moreover, when using modern packaging materials or coated card materials, on account of sliding friction this apparatus harbours the risk of damaging the coating and further mechanical problems due to the constructional size of the apparatus based on the principle.
A method for the continuous production of tubular packaging items from flat card-material blanks is described in DE 28 50 882 A1. According to this methods, when it runs through a bending apparatus a blank is bent continuously to form a cylindrical hollow item whilst forming a overlap region of the edges of the blank in the direction of transport. The overlap region is provided with an adhesive and, when the hollow item is transported away out of the bending apparatus, it is squeezed together and thus connected. A process of this type based on gradual deformation requires great outlay for transporting apparatuses and a considerable constructional length of the bending apparatus and thus also of the entire device.
GB-A 2 124 140 discloses a method of producing hollow items where blanks are processed by means of movable bending apparatuses while being transported in a bending station. A forming mandrel defines the form of the cross section of the hollow items to be produced. According to the disclosure the hollow items have a rectangular cross section. This method always uses the transfer of the carton blank from a work II to another work station llll to fold a sealing tab preparing the final step of connecting two longitudinal edges. After reaching the final position the bending operation is finished with closing the hollow item around a mandrel. A ultrasonic sealing horn serves as a connection means seaming and sealing the area of connection. This kind, of sealing doesn""t protect the cutting edge of the laminated carton blank lying inwardly for a very long time against any kind of moisture occurring from an inner filling of the container during the time of use.
There is a very large requirement for packages which are based on tubular hollow items with a wide variety of cross-sectional areas as a preproduct. The costs for the package now make up a significant portion of the cost of the packaged product. Here, it is precisely those production steps carried out away from the filling operation that make the package considerably more expensive. The object of the present invention therefore consists in providing a method and a compact apparatus with a mode of operation which is as simple and reliable as possible to improve the efficiency and thus to reduce the costs in the production of known packages which are used predominantly for liquids and/or long-life foodstuffs.
According to the invention, a method of producing tubular hollow items having the following steps is proposed:
transporting a blank, bounded by longitudinal edges, or a web of card material or the like, from which the blank is separated, into a bending station,
the blank or the web being bent by guide elements acting as a bending apparatus and
then being held stationary in the bending station and being bent by means of movable bending apparatuses into the finished shape of the hollow item and
an overlap region being formed, in which the two longitudinal edges of the blank, which are parallel to the longitudinal axis of the hollow item, are placed one on top of the other and
are connected to one another and the hollow item being conveyed out of the bending station.
The subject-matter of the invention is also an apparatus according to Claim 28 to be preferably applied to carry out the method according to the invention.
The method according to the invention achieves the object set above in that it advantageously combines a continuous bending process with a stationary bending process. In a first step of the method, the blank or a web of card material is bent continuously by means of rigid guide elements when it is introduced into a bending station. When the web has been fixed, a defined section is produced, if the card material is not used in the form of blanks. In both cases, the blank or section is already present and is held stationary in the bending station for further treatment. Movable bending apparatuses then take over the final part of the shaping operation up to the finished shape of the intended hollow item. In this case, an overlap region is formed, in which the two longitudinal edges of the blank, running parallel to the longitudinal axis of the hollow item, are placed one on top of the other and are connected to one another in a final step. The hollow item finally shaped and closed by means of these production steps can then be conveyed out of the bending station
Since, in a method according to the invention or in an apparatus constructed for its utilization, the introduction of a blank or a web is also used at the same time for prebending the card material, the operating path of the movable bending apparatuses is small compared to pressers, folding arms and the like, such as are known, for example, from DE-A 25 12 852. Any reduction in movement also reduces the wear on bearings or guides, reduces the consumption of operating auxiliaries, such as for example oils and greases, and also reduces the energy requirement of such a plant.
Furthermore, an apparatus operating according to the method according to the invention is distinguished by a small constructional size, since, in particular due to the superimposition of continuous and stationary shaping, the distances or the radius of movement and the sizes of the parts to be moved are minimized compared to the prior art. The individual steps of the method mesh with one another in an interactive manner and may also be superimposed, so that in total short cycle times can be achieved. An apparatus according to the invention can therefore also be transferred to the filling machine to produce tubular hollow items as a preliminary stage for the production of packaging items. In this case, the card material can be introduced into an apparatus according to the invention either in the form of blanks or as an endless web. The cutting unit, which is superfluous when a blank is used in the apparatus, can then slide or serve to control the dimensional accuracy of the blanks. This does not affect the extended function of the cutting unit, claimed in particular in subclaim 11 with reference to preceding subclaims, during the cutting step.
When it is supplied in the form of an endless web or a prefabricated blank, the card material is precisely positioned at the same time in the plant and is also advantageously already present by means of guide elements. These guide elements are configured in the manner of rails and have a curved section, so that they bend the present material at least partially around a mandrel. The guide elements can thus interact with the mandrel for guiding and shaping. To retain a predetermined precise position, the blank or the web is preferably clamped tightly, preferably using a presser, when it reaches a predetermined insertion length.
The blank transported into the bending station is held tightly there in a stationary manner and without further transportationxe2x80x94as in other known bending and folding devicesxe2x80x94is bent or folded around the mandrel at that location to form a tube of the respectively required cross-section by means of movable bending tools, in which case it is placed at least partially against the mandrel. This procedure permits efficient production of the tubular hollow items without considerable space requirement and outlay for machinery. The method according to the invention can therefore readily be arranged upstream of all known filling processes. The incorporation of the method according to the invention into the filling operation permits rapid reaction and adaptation of the package to different requirements, such as in particular changing package sizes and/or equipment variations. Such changes in the type of web or blanks can be carried out virtually without any outage times. For the filling operation, due to the production of the package on site, this opens up new possibilities of requirement-oriented and efficient production.
In a preferred embodiment, the bending is carried out on the present section, with the position being fixed in the apparatus, by means of bending tools which are each rotated about their own attachment points in the bending station. After the step of positioning and cutting of the web, movable bending tools thus take over the further process of shaping the blank. For this purpose, they preferably engage at least partially in a finger-like manner through the stationary elements of the bending station and, in the process, bend assigned parts of the blank.
With the completion of the bending operation, an overlap region is produced by a pressing unit in the region of the longitudinal edges with the bending tools closed. This region is connected in the bending station by being pressed together and preferably welded or bonded, so that the hollow item thus produced is fixed in a sealing manner by welding the seam of the hollow item. Precisely during welding, it is advantageous if at least part of the mandrel is arranged below the overlap region and the pressing or welding unit can thus serve as a counter-piece. For this purpose, according to Claim 7, part of the mandrel is advantageously configured as an anvil part between which and the pressing unit at least one spot-type weld of the overlap region can be carried out. According to Claim 8, this type of permanent fixing is carried out in modern, durable packaging materials, in particular by welding at least one plastic layer or plastic coating present in the overlap region.
During the fixing operation, the movable bending tools can already be opened again since the connecting region between the anvil part and the pressing unit is held securely. The finally shaped hollow item is thus secured against undesirable deviations in shape around the mandrel. By additionally opening the presser and by moving further elements, such as for example an insertion aid, back into their starting positions, a new section or part of a web can already be inserted into the bending apparatus below the hollow item to be fixed or to be welded, that is to say between the mandrel and the guide rails. Thus, in turn, two operations which are separate in terms of the process are superimposed here. Much time and energy can thus be saved, see Claims 9 and/or 10.
In the refinement of the method according to the invention, specific features have to be taken into account for packages. For instance, in the case of plastic-coated liquid packages, and in particular for packages with very long-life moist or liquid contents, it is necessary to protect at least one cut edge of the blank, located on the inside in the finished package, against the ingress of moisture or liquid into the core material. For these particular conditions of use, on packages a so-called bent-over or folded-over seam is preferably used, namely an additional longitudinal edge folded out-wards in the overlap or connecting region. In the case of card material coated with a plastic film on both sides, the longitudinal edge located on the inner side in the overlap region of the later seam is folded over towards the outside of the package and is covered by the longitudinal edge on the outside of the package. In the three-layer arrangement thus formed, the plastic coatings of the individual layers always rest against one another. These plastic layers can advantageously be connected to one another in a sealing manner, for example in a welding operation, without using an additional adhesive or further materials.
Known methods, compare for example DE 35 31 663, for producing a folded-over seam are always constructed in several steps and nevertheless ultimately provide imprecise seam points. In this case, it very often happens that the longitudinal edges of the folded-over seam to be welded are displaced relative to one another, such that the continuity in the design of the package cannot be maintained. In contrast, according to the present invention, a folded-over seam is produced in an efficient and reliable manner with a precise position in the edge region or in a central region. Based on the subsequently described exemplary embodiments, it can be seen that the method according to the invention can also be used for other package and seam shapes and seam arrangements.
According to Claim 11 in the production of a tubular hollow body with a folded-over seam, the material is prefolded during the production of a defined blank in the cutting operation in the region of the cut edge thus produced, in such a way that a first longitudinal edge is already produced here with an additional longitudinal edge prefolded on it. This longitudinal edge is advantageously used, applying a simple toggle lever mechanism, to produce the folded-over longitudinal seam on the package edge or in its central region. According to Claim 12, the additional longitudinal edge is simply formed by the fact that it is bent around a folding edge during the cutting operation by means of a top cutter. The additional longitudinal edge is advantageously determined in its width and area shape by the cross-sectional shape of the top cutter.
Furthermore, both the shaping body or the mandrel and the bending tools are adapted at their contact surfaces, at which they come into contact at least partially with the blank, to the desired final shape of the hollow item to be produced. Complete correspondence is thus not required.
For the method according to the invention and in the apparatus according to the invention, web or blank material with prestamped scoring lines can readily be used. By bending the blank around these scoring lines, very precise folding edges or corners can be produced in a simple bending process. As an alternative thereto, according to a further development of the method according to the invention according to Claim 23, scoring lines are impressed on the card material directly before the cutting operation. At the sites of these scoring lines, the material is prepared in a precisely defined manner so that edges of the later hollow item already form at the scoring lines merely due to the bending of the web or the blank in the stationary guide elements of the bending station. This bending or folding operation can be further reinforced by suitable shaping of the mandrel profile, advantageously also together with the guide elements. Correspondingly, in a method according to the invention, not only hollow items with a circular or oval cross-section, but also those with a triangular, square or rectangular or other polygonal cross-section can be produced efficiently and precisely.
A pressing unit is arranged at the bending station for acting on the overlap region of the three-dimensionally shaped blank. According to the invention, its object is to squeeze together the longitudinal edges of the blank, which are fed precisely on above the other or placed one on top of the other in the overlap region, according to Claims 15-17. By means of a multi-part construction explained below with reference to several exemplary embodiments according to the apparatus Claims 42-48, the pressing unit ensures very precise positioning of the longitudinal edges of the blank both relative to one another and in relation to the mandrel. This advantageously ensures the exact position and precise shaping of the seam on the hollow item to be produced.
According to a further development, the pressing unit is configured as a combination tool in such a way that it can carry out the prescribed positioning and squeezing of the longitudinal edges and produce a sealing weld of the longitudinal edges in the overlap region. Furthermore, the pressing unit comprises a welding tool, preferably in the form of a Sonotrode which is used at the same time as a pressing ram. In an apparatus according to the invention, in the case of a folded-over seam, external fixing and a liquid-tight connection in the overlap region are thus possible in a welding operation by welding the first longitudinal edge to a second longitudinal edge of the blank.
The supply of material can take place in an apparatus according to the invention in a known manner in the form of blanks or from a roll of an endless material web, as already explained above. Adaptation of the apparatus can be carried out quickly by setting up an insertion region on the bending station and different programming of the control. In a particularly advantageous further development, the endless web is removed from a store, for the production of which it is folded in a concertina-like manner. With concertina-like folding or fanfolding, a rectangular outside shape advantageously results for example for a wrapper as external protection and a transport and storage container of the web material. Using ordinary conveying apparatus, such as forklift trucks, etc., such wrappers can be transported and also stored more easily, in particular on pallets, than roll material. Moreover, with a fanfold, outer surfaces and inner surfaces of the later package are always in contact with one another respectively. For a hygienically satisfactory package, any transfer of soiling, for example from an outer surface to an inner surface, is thus ruled out. Simple and rapid removal or drawing-off of the web material folded in this manner results, for example, from the fact that the wrapper is opened at a top side parallel to the folded web parts located below. The web can then be pulled continuously out of the wrapper without difficulty in the direction of its longitudinal axis and fed to the bending station. However, a significant factor in the proposed storage or provision of the web material in a fanfold is the fact that, according to Claim 25, the web material is provided with a perforation in each case at the folding edge of the fanfold. During the production of the web material, this creasing region can alternatively also be provided with a semi-cut. By no means of this particular measure which can easily be integrated in the production process, the storage volume of the outer packages can be greatly increased by the higher stacking density of the material, since the creasing region located in each case at the outer edges thus does not curve up in relation to the central regions of the fanfold lying in a stack.
The web material is advantageously fed to the cutting operation directly from a wrapper. This is very simple and space-saving compared to known methods for the charging of apparatuses for the production of packaging preproducts or hollow items. In a further development according to Claim 26, the folding of the web is pulled apart in parts which each correspond to the length of a blank or a multiple of the said length. In this fixed dimension predetermined by the type of package, compact stacks are formed in a fanfold, the creasing region no longer being noticeable in the finished package or the welded hollow item.
A plurality of webs are advantageously arranged adjacently, for example in stacks, in the store or the wrapper. In particular, in this arrangement, a plurality of webs can also be removed simultaneously in parallel from the wrapper.
The applicant reserves the right to establish independent claims for the individual units of the apparatus in which steps of the method described are in each case implemented technically in an innovative manner. It is clear from the preceding description of their respective function that the advantages emerge not only in the interaction of the units in an apparatus according to the invention. On the contrary, the units can also be used advantageously in other machines, for example as a replacement for specific elements of a plant according to the prior art. The content of the claims 2-48 is incorporated herin by reference without repeating the claims.